public class ZHS{
     public static void main(String args[]){
         A a= new A();
         int [] arr = new int [args.length];
      for(int i =0;i<args.length;i++){
            arr[i] = Integer.parseInt(args[i]);
       }
           System.out.println(a.C(arr[0],arr[1]));
      }
}
class A{
       public  int  C(int n,int m){
                if(m<0||n<m||n<0)
                      return 0;
               else if(m==n)
                      return 1;
                else if(m==1)
                       return n;
                else return
                   C(n-1,m-1)+C(n-1,m);
               
        }
}


